var i = 1;
function go(){
    var num = parseInt(Math.random()*14+1)+14;
    var timer = setInterval(function(){
        num--;
        if(num==0){
            clearInterval(timer);
        }
        var items = document.getElementsByClassName('item');
        for(var item of items){
            item.classList.remove('current');
        }
        var item = document.getElementById('item'+i);
        item.classList.add('current');
        i++;
        if(i>14){
            i = 1;
        }
    },100);
}